Rifleman Q & A: Make Room For Headspace

by
posted on August 4, 2017
** When you buy products through the links on our site, we may earn a commission that supports NRA's mission to protect, preserve and defend the Second Amendment. **
headsp.jpg

Q: I have owned and handled guns for 70 years, and have never been concerned about headspace. I have three sporterized Springfield 1903s. One had a nice shiny bolt, while my favorite one had a very dull bolt. So I switched those. Should I take it out and reach around a tree to fire it? Would the brass show any problems? If headspace is so critical, how come I read about fire forming brass? How do headspace gauges work?

A: While it is never recommended that one cavalierly trade bolts between rifles, if the process is monitored and precautions are observed, it may be perfectly safe. It’s probably unlikely that your three U.S. 1903 rifles feature the bolts with which they were originally fitted, and it’s totally possible that switching bolts could actually improve the headspace dimensions of the rifles involved. A competent gunsmith with proper gauges can check the result.

Keeping within the constraints of this space, the quick and dirty definition of headspace within a firearm is the distance from the bolt face, when the bolt is locked, to a location, usually within the chamber, that provides a “stopping point,” beyond which a cartridge may no longer move, and corresponds to a position on the cartridge. For purposes of uniformity (and thereby, safety), specifications have been established for both firearms and ammunition to assure function and safety. Because absolute dimensional perfection is unobtainable in manufacturing, there are tolerance limits allowed for both gun chambers and the ammunition to fire in them. An excessive headspace condition can exist because the ammunition is “undersize.”

See the cartridge illustration for the .30-‘06 Sprg. nearby. The headspace dimension for the chamber is from the bolt face to a point on the shoulder where the diameter is 0.375". It is allowed to be from 2.0487" to 2.0587", a difference of 0.010". Gauges are available to determine whether the chamber dimensions fall within that range. This is an “ideal” range, safe and functional. Extreme variations can be dangerous. Excessive headspace conditions in a rifle can be accommodated by certain reloading techniques, as long as an excessive unsupported case situation does not exist. While “fire forming” can apply to longitudinal dimensions, it also is a feature of radial expansion.

—John Treakle, Contributing Editor

Latest

Hopkins & Allen Gunmaker
Hopkins & Allen Gunmaker

Hopkins & Allen: The Armsmaking Giant That Didn't Survive

Founded in 1868 in the northeast U.S., Hopkins & Allen grew from a friendly business venture into a prolific maker of affordable guns for brand names such as Merwin & Hulbert and Forehand & Wadsworth.

Burris Optics Celebrates 50 Years Of Fullfield Riflescopes

Firearms and ammunition ballistics have changed greatly over the last half-century, but one of the biggest leaps in performance hit the scene five decades ago, when Burris Optics introduced its Fullfield line of riflesopes.

I Have This Old Gun: Heckler & Koch P7

In the mid-1970s, the German federal police sought a replacement for its existing World War II-era sidearms and put out stringent guidelines for what it wanted in a handgun. The result was the Heckler & Koch P7.

New For 2025: Smith & Wesson Shield X

Smith & Wesson's new Shield X micro-compact handgun combines elements from the company's M&P Shield Plus with some cues from its smaller Bodyguard 2.0 design.

Review: Tisas PX-5.7 FO

The idea that a faster-moving, lightweight projectile can do the same work as a heavier, slower-moving slug has been around for ages, and the math clearly supports it, even if some in the general public don’t.

NRA Awards Grand Scholarships To 2024 Y.E.S. Students

The Y.E.S. program—which launched in 1996—is held each summer in Washington, D.C., and brings together high-achieving high school students from across the country for a week of immersive learning focused on the U.S. Constitution, Bill of Rights and American government.

Interests



Get the best of American Rifleman delivered to your inbox.